It's basically just the materiel you use to masturbate, when you are lonely at night, and regular porn doesn't fill that depressing loneliness. Imagine you are lonely and you can't cum, and you really need to feel plesure, after having a hard day. What do you do? You try something different. Often consisting of all sorts of hentai, or in very special cases, two dwars shitting in each others assholes.
Person 1: Do you have something i can beat my meat to at night?
Person 2: Yea, i have some late night meat beating materiel you can use.
Person 1: Thanks, my masturbation was getting a bit stale.